1. Field of the Invention
The present invention generally relates to a mobile communication network. More particularly, the present invention relates to a method and apparatus for registering the location of a terminal in a Packet-Switching (PS) domain of a mobile communication network.
2. Description of the Related Art
FIG. 1 illustrates a conventional mobile communication network including an enhanced Mobile Switching Center (eMSC) in a PS domain.
Referring to FIG. 1, a User Equipment (UE) 131 is connected to a call service over an Internet Protocol (IP) network 101.
Reference numeral 102 denotes a mobile communication Core Network (CN) and Access Network (AN) that has been enhanced from the European 2.5th/3rd Generation (2.5G/3G) mobile communication system, General Packet Radio Service/Universal Mobile Telecommunications System (GPRS/UMTS).
Enhanced Node Bs (eNBs) 121 through 126 manage wireless connections. Mobility Management Entities (MMEs) 111, 112 and 113 are responsible for authentication and registration of the UE 131 when the UE 131 is connected to the mobile communication network. They process a service request from the UE 131, and ensure mobility for the UE 131 when the UE 131 moves between eNBs. Although only three eNBs and six MMEs are shown it would be within the knowledge of those skilled in the art that this representation is merely illustrative of a conventional network and that then number of eNBs and MMEs may be increased or decreased without altering the scope of the invention.
Serving GateWays (SGWs) 105 and 106 provide a bearer service for transferring user service data, such as voice information, to the eNBs 121 to 126. A Packet Data Network GateWay (PDN GW or PGW) 104 allocates an IP address to the UE 131 connected to the mobile communication network and provides the UE 131 with IP connectivity. The PDN GW 104 acts as a general IP router in the IP network 101.
An eMSC 103 functions in a manner similar to that of an MSC in a 2G/3G mobile communication network, except that the eMSC 103 provides only PS service, and not Circuit Switching (CS) service, as compared to a conventional MSC that provides a CS service. In other words, the eMSC 103 transmits all call control signals and voice signals in IP packets. A benefit that the eMSC 103 offers by providing the packet service is that as the enhanced mobile communication CN supports radio resource management and data bearer management of the eMSC 103, the eMSC 103 is not connected directly to the eNBs 121 to 126. Therefore, the eMSC 103 can be installed independent of position in the IP network 101. For example, the eMSC 103 can be positioned like a typical IP server independent of a mobile communication network.
Interfaces between the eMSC 103 and the MMEs 111, 112 and 113 are used for providing seamless and reliable handover of a voice service, even when the UE 131 moves to a 2G/3G CS network. Despite the advantage that the eMSC 103 can provide services similar to those of a conventional CS network over the IP network 101, the following limitation exists.
1. although the eMSC should have an interface with every MME of the mobile communication CN, the MME is an entity close to eNBs and if the mobile communication network provides a service over a wide area, the number of MMEs increases proportionally and thus there is a difficulty in interfacing between the eMSC and all the MMEs. Since the interface between the eMSC and an MME is used to hand the UE over to the CS network, if the MME and the eMSC are physically far away from each other, the resulting communication delay may lead to handover delay or handover failure. In the case where a roaming service is to be provided with the aid of another service provider, the eMSC should be connected to an MME of the service provider. Due to the resulting complex roaming agreement, the roaming service may not be provided actually.
Accordingly, there exists a need for a technique for registering the location of a UE through a plurality of eMSCs or a plurality of General Access Network Controllers (GANCs) and a plurality of MSCs serving as a plurality of eMSCs.